Key operated lock



p ,1968 P. E.SCHWEIZER ETAL I 3,402,581

KEY OPERATED LOCK Filed Sept. 20, 1966 5 Sheets-Sheet l INVENTORS' P.-E. SCHWE/ZER THOZZZVJ JR.

ATTORNEY Sept. 24, 1968 CHWEIZER ETALN 3,402,581

I KEY OPERATED LOCK Filed Spt. 20, 1966 3 Sheets-Sheet 2 I Ml FIG. 3A

GLE LEVER NO BAFFLE PLATES OR PLUG m PLACE FIG. 5 PRIOR ART GLELEVER,BAFFLE PLATE- Y AND PLUG IN PLACE SIN 3 Sheets-Sheet 5 KEYOPERATED LOCK FIG. 44

P. E. SCHWEIZER ET AL Sept. 24, 1968 'F ild Sept. '20, 1966 l 2 H S I 33 M D :Pll L E 5 IILI J P V 2 ZWIIPMHWIIIH CLv E 2 v: 0| Fl R m Iii n 1i V 2 3 H 4 1 HUI l ll L l 6 ll-JPHH 8 W; D 5 7 N 7 5 5 E II 2 L A B N 2C D 7 4 2 .l 4 I A 6 D 1 m A C 3 G- 5 9 6 8 h 5 7 m 3 3 0 F w l. 3 I! 9l 6 2 WP 5 ti 2 l M1,; 2 k 2 I3 H. 2 l wlflfli l, 2 0 0 2\ H3 10 g KEYAND PLUG IN PLACE LEVERS AND BAFFLE PLATES REMOVED United States Patent3,402,581 KEY OPERATED LOCK Paul E. Schweizer and Richard K. Thompson,Jr., Indianapolis, Ind., assignors to Bell Telephone Laboratories,

Incorporated, Murray Hill, N.J., a corporation of New York Filed Sept.20, 1966, Ser. No. 580,707 13 Claims. (Cl. 70-355) This inventionrelates to key operated, lever type locks and its general object is toenhance the security of such locks against lock-picking and other formsof fraudulent entry.

A key operated, lever type lock typically employs a stack of pivotallymounted leaf-like levers or tumblers. Each lever has a deep notch orgate extending in more or less radially from its curved outer periphery.As the key is turned, each of the key notches engages the side edge of acorresponding one of the levers causing it to pivot through a relatedarc of travel until all of the lever gates are aligned in the path of aprojection or fence portion of the bolt.

The key is accommodated by a roughly cylindrical lock-center or plugthat rotates as the key is turned. The bottom of the plug conventionallyterminates in an integral tongue-like cam. As the cam rotates, itengages a cam follower surface on a plate that in turn is integral withthe lock bolt, withdrawing the bolt from the locked position as thefence slides into the accommodating opening provided by the alignedgates of the levers.

The basic problem of a lock-picker is to rotate each lever, without thebenefit of a key, to a point at which each lever gate is in alignmentwith the fence portion of the bolt. This problem is readily solved byskilled lockpickers by any one of a number of methods, most of whichemploy some combination of the following steps. First, pressure ortension is exerted on the movable locking members in a direction to openthe lock. This step is typically accomplished by rotating the plug andits associated cam with some suitable tool. The tension thus appliedtakes up the clearances between the lever pivot pin and the pivot holein the levers and between the fence and the top radius of the levers.Next, each individual lever is rotated with a picking tool. As the gatein each individual lever is aligned with the tool, the lever is movedfurther toward the fence by the amount of clearance between the pivothole and the pivot pin under the urging force of an individual leverreturn spring that conventionally biases each lever toward its home orlocked position. Each lever gate is aligned with the fence in the mannerdescribed and each is held in that position by the combined force of thetensioned bolt and the lever return spring associated with each of thelevers.

While picking each lever to the desired position, the lock-picker mustwork almost entirely by his sense of touch and, for a skilled picker,the clues that are provided by the feel of the lever as the gate isaligned with the fence clearly mark the position of the lever. Aparticularly useful asset to the lock-picker is the spring tension thatis uniformly exerted by each of the lever return springs that serves tomaintain each picked lever in the open position as each succeeding leveris picked.

Various attempts have been made in the prior art to make locks of thetype described more pick resistant. These attempts include the use ofbaflle plates sandwiched between adjacent pairs of levers which makespicking access to the levers more difficult. Addition-ally, it is commonpractice to employ levers with one or more randomly spaced false gates-afalse gate being a relatively shallow notch adjacent to the true gatethat tends to confuse the picker in his judgment as to the position ofthe true gate with respect to the fence. The skilled picker,

however, is generally able to circumvent such so-called pick-resistantfeatures with little or no difliculty.

The fraudulent opening of key operated locks is by no means restrictedto the use of lock-picking techniques. Assorted brute-force or refinedforce methods are employed that typically concentrate on the weak pointsof the particular lock. Various locks are available that have been maderesistant to a broad range of possible forcible entry methods byemploying very heavy, high strength materials for most or all lockparts. Such locks are inherently bulky, however, and far too costly topermit economical widespread use.

A completely secure key operated lock is of course an impossible goaland, accordingly, alarm systems are sometimes employed to provide eithera local or distant warning signal to indicate that a lock has beenfraudulently or forcibly opened. Generally, such warning systems aredeficient in that they are actuated by the movement of the bolt andhence, more often than not, the alarm merely signals the completion of afraudulent entry rather than signaling that an attempted and thereforepreventable fraudulent entry is being made.

Each of the indicated prior art problems is either overcome or at leastalleviated by a lock constructed in accordance with the principles ofthe invention. These principles are broadly directed to a philosophy oflock design that strikes a unique balance between the goal of a combinedhigh resistance to both manipulative and forcible means of fraudulententry and the goal of low cost and ease of manufacture. Insofar as pickresistance is concerned, the features of the invention are directedtoward the elimination of those structural and operating aspects ofconventional key locks upon which the picker typically relies to aid himin his task. For example, the ability of a picker to tension the lockmerely by forcibly turning the plug is eliminated by the utilization ofa floating or unattached cam that drives the bolt in response toengaging contact with the key. This floating cam is employed in lieu ofthe conventional plug-attached cam.

Another feature of the invention eliminates the individual lever springsthat so conveniently assist the picker in holding each lever inposition, after picking, with the gate aligned with the fence. Instead,a common spring assembly is employed. When picked to the open position,the lever with maximum throw removes or substantially reduces springpressure from all of the other levers. There is a tendency to overpickan unbiased or floating lever and the plug must be rotated back torestore any overpicked lever to its locked or home position.Unfortunately, for the picker, plug rotation forces all levers includingproperly picked levers, back to the locked position through the actionof a unique plug camming surface that rides against the leg of eachlever as the plug is rotated.

Another feature of the invention involves the placement of the center ofcurvature for the top edge radius of each lever. By employing leverswith different centers or curvature, the pickers feel for the positionof each lever is largely destroyed.

A further feature relating to the lever common return spring assemblyinvolves its use as a dual function device. In addition to its functionas a lever biasing means, it also actuates an alarm switch in responseto the movement of any lever, in contrast to prior art alarm switchesthat are bolt operated. It is thus possible to signal a warning that thelock is being picked rather than signaling that the lock has beenpicked.

The principles of the invention as well as additional objects andfeatures thereof will be fully apprehended from the following detaileddescription of an illustrative embodiment and from the drawing in which:

FIG. 1 is an exploded view of a lock in accordance with the invention;

FIG. 2 is an enlarged plan view of one of the lock levers shown in FIG.1;

FIG. 3A is a plan view of the interior of the lock with a lever in thelocked position;

FIG. 3B is a plan view of the interior of the lock with a lever in theunlocked position;

FIG. 4A is a plan view of the interior of the lock with the bolt in thelocked position;

FIG. 4B is a plan view of the interior of the lock with the bolt in theunlocked position; and

FIG. 5 is a partial plan view of a prior art lock illustrating the useof an individual lever return spring.

Construction and assembly As shown in FIG. 1 a lock in accordance withthe invention is housed in a steel case which includes integral mountingflanges 1111, an integral top plate 12 and a lower plate (not shown). Atotal of five mounting studs 1317 are suitably atfixed to the bottom ofthe case 10, by riveting for example. When the lock is assembled, thetop portion of each of the mounting studs 13-17 is accommodated by acorresponding one of the mounting holes 18-18 in a protector plate 19and by a correspond ing one of the mounting holes 20-20 in a lock cover21. The stud 14 also serves as a mounting for a plug spring 22 whichmaintains a lock center or plug 23 in a neutral position to permitinsertion of a key 24. The stud 15 also serves as a pivot post for alever spring assembly 25 which comprises a pivotally mounted bracket 26with an integral lip 27 which is biased by a spring 28. The lip 27 thustends to maintain each of the levers 29 in a locked position, as shownin FIG. 3A. The return spring assembly 25 also includes a bent leafspring 30 which drives a plunger 31 to actuate an alarm switch 32, asshown in FIG. 3B, in response to the movement of any of the levers 2929from its locked or home position.

The protector plate 19 is preferably fabricated from hardened tool steeland provides substantial protection against penetration by drills. Anoff-center aperture 33 provides the upper bearing surfaces for the lockplug 23. The plate 19 also acts as a force distribution member tocounteract force attacks on the lock. The force of a frontal attack froma punch, for exampl is transmitted through the protector plate 19 andthe studs 13-17 to the case 10 and then on to the mounting screws (notshown). The protector plate 19 also includes a stop pin 34 whichrestricts clockwise rotation of the plug 23 and prevents the rear of theplug from coming into contact with the through it. The keying hole 35 inthe protector plate 19 is located to the right of the plug cam 36.counterclockwise rotation of the plug 23 is restricted by the cam pin63, shown in FIG. 3A and by the bolt plate 38 so that it cannot beturned to the keying hole 35.

The plug 23, which includes a main cylindrical portion 39, an integralcam 36 and an int gral cylindrical nose 40, is designed in accordancewith the invention to provide a deep enclosed keyway 41 and to ensureseparation from the bolt actuating member or cam 37. It is of sufficientstrength to resist punch and drill attacks. When assembled, the nose ofthe plug 23 is accommodated by a hole 42 in the bolt actuating cam 37.The nose 40 also protrudes into an aligned accommodating hole (notshown) in the bottom of the case 10.

Each of the levers 2929 is mounted for pivotal movement on the pivotstud 17. Between each adjacent pair of levers 29-29 there is a bafiieplate 43 secured against movement by the studs 16 and 17. One of thebaffle plates 43-43 is mounted on top of the uppermost one of the levers29. The bafiie plates 4343 prevent interacting friction between adjacentlevers 29-29 and also prevent straight-through picking access from anupper lever to a lower lever.

Detailed construction of an illustrative lever 29 in accordance with theinvention is shown in FIG. 2. The lever 29 includes a main body portion45 and a mechanical return arm portion 46 so that it is substantially L-shaped. An open slot or gate 47 accommodates a fence leg 56 of the boltassembly 44 when the lever is pivoted to its unlocked position by theturning of the key 24. In accordance with the invention, the curvedportion 61 of the lever 29 has a radius R centered on the extended axis49 of the fence leg 56. This construction is particularly advantageousinasmuch as it ensures that the upper right corner 50 of the gate 47 andthe upper left corner 51 of the gate 47 will be substantiallyequidistant from the fence leg 56 when the lever 29 is pivoted to itsopen position, as shown in FIG. 3B. If, as in many prior art locks, thecenter of curvature is instead located at the pivot point 52 of thelever 29 with a radius R the upper left corner 51 of the gate opening isslightly higher than the right corner 50 which provides the lock-pickerwith a clue as to the lever position whenever the lever 29 is tensionedagainst the fence leg 56.

In accordance with the principles of the invention it is possible toavoid the disadvantages of the high corner effect described above bymodifying the circular contour of the lever slightly by removing thehigh corner material as shown by the hatched area if a radius such as Ror R is employed. Contact between the fence leg 56 and the lever 29 isthus held to a minimal level even when the bolt assembly 44 is placedunder tension. As a result, it is possible, in accordance with theinvention, to employ gates with varying radii of cutvature, as indicatedfor example by the radii R R and R Although a lever with a radius ofcurvature R centered as shown in FIG. 2, appears to be theoreticallyideal in that no modification of the circular contour is required,variations in lever curvature from lever to lever are employed inaccordance with the invention because they are extremely frustrating toa lock-picker. Specifically, if levers different radii are used, somelevers give the feel of a rising curvature as the lever is forcedagainst the fence, other levers give the feel of a falling curvatureunder these same conditions, and levers with centers of curvature on theextended axis of the fence give a balanced feel when aligned.

In addition to its true gate 47, each lever 29 includes one or morefalse gates 53 as shown in FIGS. 2, 3A and 38. False gates are typicallymade slightly wider than true gates and are randomly positioned toenhance the possibility that a lock-picker may mistake the false gatefor a true gate.

The bolt assembly 44, best shown in FIG. 4A, includes a bolt proper 54,which is accommodated by a strike aperture (not shown) to provide thebasic locking connection, a fence 48 and a bolt plate 38. The bolt fence48, the bolt plate 38 and the bolt 54 are integrally connected bybrazing or welding. The fence 48 has a first leg 56 (which by itself mayproperly be identified as the fence) that is accommodated by the gates4747 of the levers 2929 when the levers are moved to the unlockedpositioned, and a second leg or lug portion 57 which limits pickingaccess to the top radius portion of the levers. The bolt plate 38 is insliding contact with the bottom of the case 10 and its positioning iscontrolled in part by the slot 58 that accommodates the lever pivot stud17. The bolt plate 38 has an open center portion with cam followersurfaces A, B, C and D that are engaged by the bolt actuating cam 37 ina manner described hereinbelow under Operation. The cam 37 has acircular aperture 42, which, as indicated above, accommodates the nose40 of the plug 23, and a slot 62 which accommodates the key 24. The pin63 on the cam 37 is engaged by the cam 36 of the plug 23. The purpose ofthis engagement is to orient the key slot 62 of the cam 37 intoalignment with the key slot 41 of the plug 23 when the plug 23 is turnedto its vertical or locked position. Without this feature, tamperingcould misalign these two key slots 62 and 41 and thus prevent insertionof the key.

Operation Assume that the lock is in the locked position and that thekey 24 has been inserted in the plug slot 41, as shown in FIG. 3A. Asthe key 24 is turned to the right or clockwise, each of the key notches64 engages a corresponding one of the levers 29--29 on its left edge,causing it to pivot against the biasing force of the lever spring 28 ofthe spring assembly 25. If instead, an attempt is made to pick the lockwithout the use of a proper key and each lever is successively moved tothe right, the spring return effect of the spring assembly 25 will givea different feel to a picker, depending upon the sequence in which thevarious levers 2929 are moved. If a maximum trave lever, for example, ispicked first, pressure on the remaining levers 2929 is removed, thusgiving the effect of floating or friction levers. If a minimum travellever is positioned first, then the spring or friction feel of the nextlever will depend upon the angular distance through which that lever ismoved. At first, no spring action is felt. As the lever is moved pastthe position of the first or minimum travel lever, however, spring biasis applied increasingly until the full spring force is brought to bearagainst the second lever. Spring force against successively positionedlevers depends upon the angular throw of each. With a key, however, thevarying spring forces exerted on each lever are of no consequence andeach of the levers is pivoted so that all of the gates 4747 are alignedwith the fence leg. 56. One lever 29 is shown positioned in this mannerin FIG. 3B.

As the spring assembly 25 is pivoted, the leaf spring 30 is forcedagainst the plunger 31 causing the switch 32 (FIG. 3B) to operate. Tosimplify the view presented in FIG. 4A, the switch 32 is shown mountedoutside the case 10. It is of course possible to employ a switch smallenough to be positioned inside the case. Operation of the switch 32 isutilized to initiate a suitable warning signal which may be either localor which may be transmitted to a central point over a telephone line if,for example, the lock is used for a telephone coin box.

Continued turning of the key 24 after the gates 4747 have been alignedwith the fence leg 56, forces the cam 37 to rotate clear of the camlocking surface A until it impinges against the cam follower drivingsurface C which drives the bolt assembly 44 and thus the bolt 54inwardly to its unlocked position as shown in FIG. 4B. The final portionof travel of the cam 37 brings it into contact with the cam followerlocking surface D, as shown in FIG. 4B.

In locking the lock, the key 24 is rotated counterclockwise so that thecam 37 clears the cam follower surface D of the bolt plate 38 and bearsagainst the cam follower driving surface B which drives the boltassembly 44 and thus the bolt 54 outwardly to the locked position, asshown in FIG. 4A. At the end of its travel, the cam 37 comes to restagainst the cam follower locking surface A, as shown in FIG. 4A. At thesame time, the combined action of the spring assembly 25 and the plugcam 36 impinging against the arms 46 of each of the levers 2929 ensuresthat each lever is driven to its fully locked position, as shown in FIG.3A. This action is in contrast to the lever return action of prior artlocks, as shown in FIG. 5, where each lever 65 is individually biased tothe locked position by a respective return spring 66. Individual returnsprings, which have been eliminated in accordance with the invention,are an asset to the lock-picker because of the steady force they supplyto hold each lever against the gate once the lever has been picked toits unlocked position. As previously explained, in a lock in accordancewith the invention, spring ten sion is applied only against the leversof maximum travel when the levers are moved to their unlocked positions.

It is to :be understood that the embodiment described herein is merelyillustrative of the principles of the invention. Various modificationsthereto may be effected by persons skilled in the art without departingfrom the spirit and scope of the invention.

What is claimed is:

1. In a key operated lock, in combination, a bolt including a fenceportion, a plurality of pivotally mounted levers each having a gate foraccommodating said fence portion when said bolt is in its unlockedposition, the pivot of each lever being spaced from the extended axis ofsaid fence portion, each of said levers having a substantiallycircularly curved edge portion adjacent to said gate, the center ofcurvature of said circularly curved portion for at least one of saidlevers being on the extended axis of said fence portion and differingfrom the center of curvature of said circularly curved portions ofothers of said levers.

2. Apparatus in accordance with claim 1 wherein the center of curvatureof said circularly curved portion for at least one of said other leverscoincides with the pivot point of said last named lever.

3. In a key operated lock, in combination, a bolt including a fenceportion, a plurality of pivotally mounted levers each having a gatetherein to accommodate said fence portion when said bolt is in itsunlocked position, a spring loaded member normally urging all of saidlevers to a locked position, said member being tensioned by any one ofsaid levers that is moved toward an unlocked position thereby removingspring tension from all the other of said levers, whereby said lastnamed levers are free to move toward an unlocked position without springbias.

4. Apparatus in accordance with claim 3 including an alarm switchresponsive to the movement of any one of said levers to the unlockedposition.

5. Apparatus in accordance with claim 3 including an alarm switchoperatively responsive to said spring loaded member whenever said memberis tensioned by the movement of any one of said levers toward itsunlocked position.

6. In a key operated lock, in combination, a bolt including a fenceportion, a plurality of pivotally mounted levers each having a gatetherein to accommodate said fence portion when said bolt is in itsunlocked position, spring loaded means normally biasing all of saidlevers in the locked position, the bias of said spring loaded meansbeing removed from all but one of said levers when said last named leveris moved to the unlocked position, said spring loaded means tending todrive all of said levers back toward a locked position upon thewithdrawal of said fence from said gates.

7. Apparatus in accordance with claim 6 wherein each of said leversincludes a respective extended portion having a cam follower surfacethereon, a plug member for accommodating a key, said plug memberincluding a cam portion, said cam portion drivingly engaging said camfollower surface on each of said levers and driving said levers to thefully locked position in response to the turning of said key in saidplug toward the locked position.

8. In a key operated lock, in combination, a bolt including a strikeengageable tongue portion, a fence portion and a cam follower plate, aplurality of levers each including a gate for accommodating said fenceportion when said lock is in the unlocked condition, a free floating camhaving a slot therein for accommodating a key,

a plug for accommodating said key, said cam drivingly engaging said camfollower plate to drive said bolt to a locked position or to an unlockedposition in response to the turning of said key in the locked orunlocked direction, the end of said plug being freely rotatable in thecenter of said cam without drivingly engaging said cam.

9. Apparatus in accordance with claim 8 wherein said cam includes anintegral pin engageable with a cam portion of said plug to ensure properorientation between the key slot of said plug and said slot in saidfloating cam.

10. Apparatus in accordance with claim 8 wherein said cam follower platehas an open center portion, the inside edge of said open center portionforming a plurality of cam follower surfaces engageable by said floatingcam, said cam being positioned in said open center portion in a planecommon with said plate.

11. Apparatus in accordance with claim 8 wherein said plug includes acam portion for driving said levers to a fully locked position as saidplug is turned to the locked position.

12. In a key operated lock, in combination, a bolt including a strikeengageable tongue, a fence and a cam follower plate having an opencenter portion with a bounding interior cam follower surface, aplurality of pivotally mounted levers each including a first extendedleg having a cam follower surface and a second extended to thecompression of said spring assembly as any one of said levers is movedto the unlocked position, a key accommodating plug having a cam surfaceengageable with said cam follower surface of each of said levers wherebysaid levers are driven to the fully locked position by the turning ofsaid plug, and a floating cam having a key engageable aperturepositioned in said center portion of said plate and responsive to theturning of said key when engaged therein for driving contact with saidcam follower surface, thereby extracting or extending said bolt inresponsive to the direction in which said key is turned.

13. Apparatus in accordance with claim 12 wherein said center ofcurvature for said one of said levers that is off said extended axis ison the pivot point of said last named levers.

References Cited UNITED STATES PATENTS 697,568 4/1902 Treat 703551,957,586 5/1934 Gutman 70355 2,524,696 10/1950 Ellis 70355 X OTHERREFERENCES DAS 1,152,035, July 1963, German printed application(Albers), 70-392.

MARVIN A. CHAMPION, Prinmry Examiner.

P. TEITELBAUM, Assistant Examiner.

1. IN A KEY OPERATED LOCK, IN COMBINATION, A BOLT INCLUDING A FENCEPORTION, A PLURALITY OF PIVOTALLY MOUNTED LEVERS EACH HAVING A GATE FORACCOMMODATING SAID FENCE PORTION WHEN SAID BOLT IS IN ITS UNLOCKEDPOSITION, THE PIVOT OF EACH LEVER BEING SPACED FROM THE EXTENDED AXIS OFSAID FENCE PORTION, EACH OF SAID LEVERS HAVING A SUBSTANTIALLYCIRCULARLY CURVED EDGE PORTION ADJACENT TO SAID GATE, THE CENTER OFCURVATURE OF SAID CIRCULARLY CURVED PORTION FOR AT LEAST ONE OF SAIDLEVERS BEING ON THE EXTENDED AXIS OF SAID FENCE PORTION AND DIFFERINGFROM THE CENTER OF CURVATURE OF SAID CIRCULARLY CURVED PORTIONS OFOTHERS OF SAID LEVERS.